The pathogenic potential of anaerobic corynebacteria in relation to periodontal disease has not been investigated despite their relatively large number in the gingival crevice. Anaerobic corynebacteria have a predilection for infecting the reticulo-endothelial system (RES), lodging in lymph nodes or in bone marrow and producing granulomatous reactions. Infection with these organisms results in hyperfunction of the RES as measured by phagocytic index and antibody, and interferon production. Corynebacterium acnes, an anaerobic corynebacterium is found in man as a resident of the oral and skin microflora. Its ability to influence the immune response may be a factor in initiating or exacerbating the inflammatory processes in periodontal disease. The ability of C. acnes to influence local antibody response to antigens introduced into the oral mucosa of experimental animals will be studied. The role of C. acnes in human periodontal disease will be investigated by testing human subjects for cellular and humoral immunity to this organism.